CN106066511B

CN106066511B - Fiber-optic device and method for producing such a device

Info

Publication number: CN106066511B
Application number: CN201610510485.8A
Authority: CN
Inventors: R·阿加诺格鲁; H·阿伦特; A·海因策; B·库尔特
Original assignee: Leoni Kabel GmbH
Current assignee: Weilede Industrial Co ltd
Priority date: 2015-04-24
Filing date: 2016-04-22
Publication date: 2021-02-19
Anticipated expiration: 2036-04-22
Also published as: US10018784B2; CN106066511A; US20160313506A1; DE102015207611A1; EP3086144B1; EP3086144A1

Abstract

The invention relates to a fiber-optical device (2) for radially coupling out Light (LT), particularly for medical or industrial applications, comprising an optical fiber (4) which extends in a longitudinal direction (L) to a distal end (6) and has a core (14), and comprising a diffusing section (7) in which a plurality of macroscopic scattering elements (18) are arranged, which each protrude into the core (14), and to a method for producing such a device (2).

Description

Fiber-optic device and method for producing such a device

Technical Field

The present invention relates to a fibre-optic device and a method for manufacturing such a device. The fiber-optic device is also referred to as a diffuser.

Background

Fiber-optical devices are used above all for emitting light into a defined spatial region and are generally used for irradiation within the scope of medical methods, for example for thermally treating or ablating tissue, in particular in vivo applications, but also in vitro applications in alternative applications.

The device generally comprises an optical fiber into which light is coupled at a first end, which is usually connected to a light source. The coupled-in light is first guided in the longitudinal direction of the fiber to the distal second end and is coupled out of the fiber in the radial direction at a suitable point in the diffusing section, typically at or near the distal end. For this purpose, the fibers must be prepared accordingly at this point in order to reduce the total reflection in the interior of the fibers that is normally used for light conduction and instead to couple out at least part of the light in the radial direction.

For example, according to US2009/0210038a1 scattering particles are known which are embedded in the fibers and scatter the light guided in the fibers in such a way that the total reflection angle is not exceeded and thus the light is coupled out of the fibers in the radial direction to an increased extent.

Disclosure of Invention

Starting from this, the object of the invention is to provide an improved fiber-optic device which ensures a light emission which is as uniform as possible in the diffuser region during operation. Furthermore, a method for producing the device that is as simple as possible should be specified.

According to the invention, this object is achieved by a fiber-optic device according to the invention for radially coupling out light. The device is designed as a probe that can be inserted into a cavity, comprising an optical fiber, which extends in the longitudinal direction to a distal end and has a core, and comprising a diffusion section, in which a plurality of scattering elements are arranged, which each protrude into the core, wherein the fibers have a diameter in the range from 125 to 1500 μm, wherein the scattering elements each have a recess, wherein a scattering material is applied at least locally to the fibers, which scattering material has a matrix with scattering particles embedded therein for scattering light, wherein the recesses are filled with the scattering material and/or the fibers are continuously coated with the scattering material. Fiber-optic devices are particularly suitable for medical applications. The device has an optical fiber extending longitudinally toward a distal end and having a core. Furthermore, the fiber has a diffusing section in which a plurality of macroscopic scattering elements are arranged, which each project into the core, the device being used to radially couple out light.

The advantages achieved with the invention are in particular: the scattering element can be produced particularly easily, preferably by means of a laser machining method, on the one hand, and on the other hand, a particularly controlled emission of light in the radial direction can be achieved. The scattering elements in particular each have a macroscopic extent, wherein "macroscopic" in particular means: the extension or size of the individual scattering elements is significantly larger than the wavelength of the light guided in the core, preferably 1 to 4 orders of magnitude larger, in particular 2 to 3 orders of magnitude larger. The scattering element forms a boundary surface with the core, which is oriented in such a way that the incident light enters in an angular range that does not satisfy the conditions for total reflection. At these boundary surfaces, the light guided in the core is deflected or scattered, so that a larger proportion of the light is coupled out of the fiber in the radial direction, i.e. transversely to the longitudinal direction, and into its surroundings than in a fiber without scattering elements. The scattering elements then advantageously form, in particular, in each case one type of microlens on account of the boundary surfaces and their light-refractive properties.

Furthermore, a suitable design of the scattering element with respect to its size, geometry and position relative to the fibers achieves a particularly uniform emission according to a particularly uniform, in particular constant intensity distribution. In this case, the scattering elements are in particular embodied as individual, discrete depressions, recesses or indentations distributed over the surface, i.e. the fiber surface. The surface of the fibers is thus in particular structured in the diffusing zone.

In particular, due to the radially uniform light emission over the diffusing section, the device as a whole is in particular also referred to as diffuser. In operation, light is then coupled in from the light source at the first end of the fiber. For this purpose, a suitable coupling or plug connection is provided and preferably also arranged on the first end, also referred to as the proximal end or coupling end, which enables the connection of the fibers to the light source. The light source is preferably a laser or alternatively a lamp and in particular has a central wavelength in the range of 400 to 2300 nm. The fibers typically have a diameter in the range of 125 to 1500 μm, in particular 500 to 700 μm.

Light coupled into the fiber first propagates longitudinally from a first end of the fiber to a second end, also referred to as a distal or outcoupling end. The fibers up to the diffusing section are therefore expediently designed as normal fibers for light conduction by means of total reflection, up to the normal or introduction section, and for this purpose in particular have a jacket with a lower refractive index surrounding the core.

Preferably, the fibers are made of quartz glass, wherein the mantle is made of quartz glass treated with a fluoride. In one suitable alternative, only the core is made of quartz glass and is surrounded by a jacket made of a polymer, for example a fluoropolymer. The fibers are then in particular so-called PCS fibers, i.e. plastic-clad quartz fibers, or HPCS fibers, i.e. hard plastic-clad quartz fibers. Also suitable in principle are fibers made entirely of polymers, so-called polymer optical fibers, abbreviated POF.

The diffusing section is connected to the normal section in the longitudinal direction, is preferably arranged on the end side on the fiber and thus forms an end section of the fiber. The diffusion section is preferably a few centimeters to a few tens of centimeters long and in particular approximately 1 to 30cm or 1 to 10cm long. The device is then particularly suitable for in vivo medical applications, for example for ablating tumour tissue or calcification on the inner wall of blood vessels.

The scattering element serves in particular to disturb the usual light transmission by means of total reflection and thus advantageously to generate a light scattering and outcoupling from the fiber that increases the measurement at the diffusing section. This effect is produced primarily by the boundary surfaces of the scattering element, which extend from the surface of the fiber through the sheath and up to the core.

In a first preferred variant, during the production of the device for forming the scattering element, in particular, the normal fibers in the region of the scattering element to be produced are destroyed and at the same time the fiber material is removed, so that corresponding recesses are then machined into the fibers. The scattering elements in this embodiment each have a recess. The recess is first filled, in particular with air, so that a boundary surface with a corresponding refractive index difference is formed between the recess and the core. In this case, the course of this boundary surface advantageously differs greatly from the course of the boundary surface between core and cover, which is generally oriented longitudinally, so that the light guided in the core impinges on this newly created boundary layer at a corresponding further angle.

In a second preferred variant, the scattering elements are each formed as regions of the core having a modified refractive index. The respective regions are separated from one another in particular spatially. By means of such a local refractive index change within the core, boundary layers are then advantageously formed between unaffected sections of the core and the corresponding regions, which boundary layers, as already described above in connection with the recesses, lead to a deflection of the light guided in the core. Thereby, the fraction of light scattered out of the fiber is significantly increased.

In principle, different methods are suitable for producing the changed refractive index. The first method consists in machining the fibre with laser radiation, by means of which localized heating of the fibre is preferably achieved, so that the material structure and thus the refractive index of the core are brought aboutVarying in the area being illuminated. The core is melted or fused to some extent locally, i.e. in the region of the subsequent scattering element. The fibers then each have, as scattering elements, regions of the core which have been heat-treated, in particular by laser treatment. Thus, the laser machining is preferably substantially thermal. For this purpose, CO is particularly suitable, for example₂A laser. In a second method for changing the refractive index, a local ion implantation is carried out for forming a region with a changed refractive index. The fiber then has corresponding scattering elements made of the core with the addition of ions of the additional material.

In order to further improve the scattering of light, in a preferred embodiment, a scattering material is applied, in particular at least in places, to the fibers, the scattering material having a matrix with scattering particles embedded therein, in particular in the region of the scattering element. The scattering particles are used here for scattering light. The light coupled out of the fibers is then advantageously additionally scattered by the scattering particles, thereby improving the uniformity of the emission of the light in the diffusing zone. Since the light is coupled out in an enhanced manner in the region of the scattering element, it is particularly expedient for the scattering material to be arranged in this region.

In an advantageous embodiment, the recess is filled in particular completely with the scattering material. In this way, the light coupled into the respective recess on its surface is additionally scattered in an advantageous manner and the emission of the light is therefore generally more uniform. Furthermore, the filling of the recesses with material also prevents the penetration of dirt or impurities in an effective manner and also prevents the performance degradation which may occur with this, for example due to light absorption.

In a particularly preferred embodiment, the fibers are continuously coated with the scattering material, i.e., continuously coated on the diffusing regions and in particular not on the normal regions. This continuous coating of the scattering material acts to some extent as a scattering hood surrounding the fibers in the region of the diffusion section, preferably producing, on the one hand, a particularly flat surface of the fibers, i.e. in particular a constant diameter of the fibers, and, on the other hand, particularly uniform emitted light not only in the region of the scattering elements but also in the free regions located therebetween. Furthermore, the continuous application of the scattering material is much simpler in terms of production technology than the application only locally. In a preferred manner, the scattering material is applied with a wall thickness in the range of 1 to 10 μm.

In a preferred manner, in particular before the application of the scattering material, the covering of the fibers is removed at least in the region where the scattering material is subsequently applied. The scattering material is then applied directly to the core. The evanescent region of the light guided in the core then penetrates directly into the scattering hood made of scattering material, without being additionally spaced apart from the scattering hood by the now removed hood. In this way, the scattering effect of the scattering material is significantly enhanced. In this case, fibers with a sheath made of a polymer are particularly preferred, since the polymer is particularly easy to remove. Alternatively, the fibers without the cover are used directly as the initial product for making the device.

Preferably, the scattering particles are configured as nanoparticles, i.e. in particular as radicals having a spatial extent of less than 1 μm, i.e. of the order of the maximum of the wavelength of the light to be scattered, and even lower. In a preferred embodiment, the nanoparticles have an average diameter in the range from 10 to 100nm, particularly preferably in the range from 20 to 50nm, and are therefore in particular one to two orders of magnitude smaller than the wavelength of the light to be scattered. The scattering on these nanoparticles then mainly involves rayleigh scattering, while the size of the scattering elements is larger than the wavelength of the light and causes mie scattering in particular. The combination of such microscopic nanoparticles and macroscopic scattering elements as scattering centers with respect to the wavelength of the light results in an optimum homogenization of the light emitted by the device in the diffusing zone and in a particularly constant intensity distribution in the longitudinal direction.

Suitable nanoparticles are particles made of metal oxides, in particular aluminum oxide, which is particularly inexpensive and furthermore has advantageous chemical properties when embedded in a matrix of a scattering material. The matrix preferably consists of a base material which is transparent to the light conducted in the fibers, i.e. in particular has an absorption of less than 10%. In a preferred manner, the substrate is made of a material suitable for producing an optically effective fiber coating, in particular a polymer, i.e. a plastic, for configuring the fiber as a PCS fiber, i.e. a plastic-clad quartz fiber, or as an HPCS fiber, i.e. a hard plastic-clad quartz fiber. In particular in combination with fibers at least the core of which is made of quartz glass, a particularly stable mechanical connection is obtained when the recess is filled with a polymer-based scattering material. Furthermore, due to the similar materials here, particularly few defects are produced on the boundary layer between core and recess, thus preventing excessive absorption of light. In addition, this also advantageously prevents the device from heating up excessively during operation and possibly being damaged as a result. In particular in the case of light intensities in the range of approximately 10W of power, which are generally preferably used, the increased absorption of light in the fibers may lead to damage.

The proportion of the scattering particles in the entire scattering material is suitably in the range of several vol.%, preferably in the range of 1 to 10 vol.%, in particular in the range of 2 to 5 vol.%, in particular in the range of 3 vol.%. This ensures an optimum transparency of the scattering material as a whole and at the same time a suitable scattering action. The remaining portion is expediently only the base material.

Preferably, the scattering elements are spherically formed, as a result of which a boundary layer is obtained which leads to optimum scattering of light during operation. Spherical in this context means in particular that the respective scattering element in principle forms a curved boundary layer which preferably generates an imaginary sphere or a generally ellipsoid, but only substantially spherical or ellipsoidal, since the edge position is not exactly spherical or ellipsoidal. Due to the edge position, the scattering element usually has a shape corresponding to a truncated sphere or a truncated ellipsoid. The scattering element can be almost radially cut through the limited spatial extent of the fiber, so that a part of an imaginary sphere (generally an imaginary ellipsoid) lies outside the fiber and the scattering element is, for example, initially formed as a radially open cavity or cavity in the fiber. In this case, the truncated portion of the imaginary sphere is preferably significantly smaller than the actual scattering element. In other words, the scattering element has a diameter measured radially which is smaller than the sphere diameter of an imaginary sphere generated by the boundary layer due to the edge position, wherein the diameter is at least 50% and preferably at least 75%, particularly preferably at least 90%, of the sphere diameter.

The scattering element is generally preferably produced by spot machining with a laser beam. As an alternative to such a punctiform, substantially spherical scattering element, the scattering element is designed as an elongated extension, for example as a cutout. In a further suitable alternative, the scattering element is designed as a closed, radially arranged ring and therefore acts in particular in the manner of a cylindrical lens.

The scattering elements preferably have an extension of 20 to 500 μm, in particular 150 to 300 μm. In a substantially spherical scattering element, the size corresponds to the diameter of a sphere. In the case of an elongated scattering element, for example a cutout, the extent corresponds to the longitudinal extent, i.e. in particular the longest extent. The scattering element is then in particular approximately one to two orders of magnitude larger in the wavelength of the light and thus has a macroscopic size. The extension is then preferably approximately one tenth to one half of the diameter of the fiber, compared to the fiber. The diameter is preferably in the range from 125 to 1500 μm, in particular in the range from 500 to 700 μm.

In a fiber with a sheath (also referred to as cladding) surrounding the core, the core has a core diameter and the sheath has a sheath thickness, which corresponds, for example, to at least one twentieth of the core diameter and maximally to half the core diameter. Typical suitable fibers have, for example, a core diameter of 600 μm and a mantle thickness of 30 μm, i.e. a fiber diameter of 660 μm. The diameter of the sheath, i.e. the diameter including the sheath, in particular the ratio of the fiber diameter to the core diameter, is also referred to as CCDR, more precisely the ratio of the cladding to the core diameter. Here, the diffusion zones described herein are independent of a particular CCDR value. However, the fibers preferably have a CCDR value in the range of 1.04 to 9.8, in particular 1.04 to 2.5.

The scattering elements project radially into the fiber at a defined depth. The depth is measured in the radial direction, i.e. perpendicular to the longitudinal direction. Due to the edge position mentioned above, the depth is smaller in the case of a spherical scattering element than the extent of the scattering element in the longitudinal direction. Suitably, the scattering elements have a depth in the range of 15 to 450 μm, in particular 100 to 250 μm. In particular in scattering elements with recesses, which in this way for the purpose of filling with scattering material achieve particularly good accessibility, the recesses then have, in particular on the fiber surface, sufficiently large openings or holes for filling.

For a particularly homogeneous, i.e. diffuse, light emission, it is of particular importance to distribute the scattering elements along the diffusion section. In order to emit light uniformly in the radial direction, the scattering elements are therefore expediently arranged distributed in the circumferential direction as well as in the longitudinal direction of the fiber. By being distributed in the circumferential direction, particularly uniform emission in the radial direction is achieved; by being distributed in the longitudinal direction, a particularly uniform emission in the longitudinal direction is achieved in each case. For this purpose, in one suitable embodiment, the scattering elements are arranged around the fibers such that two adjacent scattering elements are arranged offset with respect to one another both in the circumferential direction and in the longitudinal direction. In one suitable alternative, the respective two scattering elements are arranged oppositely in the longitudinal direction as a pair at the same length position and subsequently a pair is arranged rotated by, for example, 90 ° in the circumferential direction.

As the light propagates through the diffusing section, the light fraction which is further directed in the distal direction is significantly reduced due to the radial emission. However, in order to ensure uniform scattering intensity in the radial direction along the entire diffusion section, the scattering elements are expediently spaced apart from one another in the longitudinal direction at variable distances.

The scattering elements are preferably spaced apart with respect to each other in the longitudinal direction at a pitch in the range of 100 to 1000 μm. This means that, in particular, an optimum scattering intensity is achieved with respect to the intensity of the further guidance, in particular if the length of the diffusion section, i.e. the diffusion length, lies within the preferred ranges already specified above.

Particularly preferred is a design in which the distance decreases towards the distal end, i.e. a larger and larger proportion of the light still guided is scattered out of the fiber towards the distal end. In general, the distance between two radially successive scattering elements decreases in a preferred manner by at least 1% to a maximum of 70%, in particular by at least 5% to a maximum of 50%, in particular a maximum of 30%, towards the distal end. In a suitable embodiment, the distance is continuously reduced, i.e. already with respect to the respective last distance. In a second suitable embodiment, the diffusing section has a plurality of subsections, wherein the scattering elements are equally spaced apart from one another on a respective subsection, but the spacing in the following subsection is reduced relative to the spacing of the preceding subsection. However, the spacing between two scattering elements does not change in a respective subsection. This simplifies the production of the diffusing section in particular. For example, the diffusion section has three subsections, each of which has, for example, ten scattering elements, wherein the longitudinal distance between two adjacent scattering elements is 600 μm at the first subsection, 550 μm at the second subsection and only 200 μm at the third subsection, in particular the distal subsection.

In principle, depending on the application of the device, a suitable embodiment is also conceivable in which, although a uniform light emission takes place in the longitudinal direction, no uniform light emission takes place in the radial direction, i.e. the scattering elements are distributed appropriately only in the longitudinal direction and not in the circumferential direction. Such a device therefore has a preferred direction in the radial direction, emitting in the circumferential direction only within a certain and limited angular range. Such a device is particularly suitable for lighting applications.

In particular when the device is used in a medical context, in particular in vivo applications, the fibers and in particular also the scattering screen are surrounded in a suitable manner by a screen which is preferably made of a material which is compatible with the substance. The cover forms the outermost layer and the boundary of the device, in particular at least over the diffusion section, and is potentially in contact with the surroundings during operation. The material is therefore suitably chosen at this angle, but at the same time sufficiently transparent to ensure that light is also emitted in the radial direction.

Particularly preferred is an embodiment in which the outer cap is a glass capillary closed at the end, i.e. at the distal end, which is characterized in particular by its biocompatibility and is furthermore particularly stably connected to a scattering cap made of silicone during production. Alternatively or additionally, a metal coating, for example made of gold, is also provided, which preferably has a layer thickness of at most 500 nm.

The device is preferably used in the field of medical diagnostics, medical treatment, illumination or inspection or processing of components or workpieces or in general in medical or industrial applications. Due to the only small radial dimensions of the fibers and the functional coverings and/or coatings arranged around them, the device is suitable, in particular in the case of a design designed as an endoscope or in the case of a probe that can be inserted into a cavity, for examining or treating difficult-to-access areas, for example for ablating calcifications in blood vessels or for irradiating intestinal tumors. However, the use of the device, in particular as a probe, is not limited to medical applications. In particular, the device is also suitable for industrial applications. Such industrial and non-medical applications are, for example, monitoring the combustion process in the interior of internal combustion engines. The device expediently additionally comprises a control or monitoring unit with a connection for the fibers, which is suitable for the application.

The object is also achieved by a method for producing a fiber-optic device according to the invention. Wherein a fiber is first provided and a plurality of recesses are machined into the fiber by means of a laser, wherein a scattering material is then applied at least locally to the fiber and/or the recesses are filled with the scattering material when the scattering material is applied. Furthermore, what has been said above in relation to said device also applies to said method in a sense and vice versa.

In order to produce the device, a fiber, in particular optical, i.e., designed for conducting light, is first provided, into which a plurality of scattering elements are machined by means of a laser. The use of a laser considerably simplifies the production and additionally leads to a particularly precise design of the scattering element. During laser processing, the material of the fiber is removed or heat-treated, in particular by ablation, and in this way, in particular substantially spherical scattering elements are producedAnd (3) a component. The processing is preferably carried out in the radial direction, so that the scattering elements project from their fiber surface into the interior, i.e. into the core, in the edge position of the fiber. In this case, openings or holes are produced in particular on the fiber surface, through which the ablated material escapes and through which the scattering element is then accessible. In a preferred manner, CO is used as a laser for machining₂Laser, the CO₂The laser enables particularly efficient processing because of the CO₂The laser radiation of the laser is particularly well absorbed by the fiber, more precisely the fiber material.

In a particularly simple embodiment, the laser is operated in pulses or pulsed mode and is moved relative to the fiber, so that a plurality of injection points distributed along the fiber are obtained, at which the scattering elements are each formed. By rotating the fiber, a plurality of scattering elements are then arranged distributed along the circumference of the fiber, simultaneously or in another alternative.

In a preferred embodiment, the scattering material is applied at least locally to the fibers.

In a further preferred embodiment, the scattering element is filled with the scattering material during the application of the scattering material.

The diffusing zone and its production are advantageously independent of the detailed construction of the fiber, in particular its CCDR and its numerical aperture. Thus, a wide range of common fibers may be used as the starting fibers and provided with diffusing sections in the manner described above. The manufacturing method is therefore particularly flexible.

Drawings

Embodiments of the present invention are explained in detail below with reference to the drawings.

Figure 1 shows a fibre-optic device,

figure 2 shows a scattering element of the device,

figure 3a shows a front view of a variant of the arrangement of a plurality of scattering elements,

figure 3b shows a side view of the arrangement according to figure 3a,

figure 3c shows another variant of the arrangement of a plurality of scattering elements,

FIG. 4 shows calculated light scattering in the radial direction as a function of position in the longitudinal direction for one embodiment of the apparatus, and

fig. 5a to d show steps of a method for manufacturing the device.

Detailed Description

Fig. 1 shows a fiber-optic device 2, which is designed in particular as a medical treatment device. The device 2 comprises a fiber 4 having a diffusing section 7 at a distal end 6. At the other end, also referred to as the coupling end 8, the fiber 4 has a first coupling element 10a, by means of which the fiber 4 is connected to a second coupling element 10b of the control unit 12.

The fiber 4 extends in the longitudinal direction L from the coupling end 8 to the distal end 6 and comprises a core 14, in particular a central core, and a cover 16 surrounding the core for conducting light in the longitudinal direction L by means of total reflection on a boundary layer between the core 14 and the cover 16. The diffusion section 7 is arranged at the end side of the fiber 4 and additionally has a plurality of scattering elements 18, which are arranged distributed in the longitudinal direction L. Furthermore, on the diffusing section 7, a scattering material 20 containing a large number of scattering particles 22 is applied to the fibers.

The respective scattering element 18 here comprises a recess 24 which extends from the fiber surface O through the cover 16 into the core 14. The recess 24 is substantially spherical in shape here and has a defined extent D, which corresponds here to the diameter of an imaginary sphere. Furthermore, the recess 24 has a defined depth T or a depth into the fiber 4 in the radial direction R, i.e. perpendicular to the longitudinal direction L, which is less than the extension D due to the edge position of the recess 24 with respect to the fiber 4, which can be seen particularly clearly in fig. 1. In the embodiment shown here, the extension D is approximately 220 μm and the depth T is approximately 200 μm. The fibers 4 generally have a fiber diameter F here corresponding approximately to 660 μm, wherein the mantle 16 has a wall thickness W of approximately 30 μm and the core has a core diameter K of approximately 600 μm. The entire diffusing section here has a diffusing length DL of approximately 5cm, whereas the entire fiber 4 is significantly longer and for example approximately 50cm (measured from the coupling end 8 to the distal end 6).

The scattering material 20 is applied continuously to the fibers 4 here, i.e. completely surrounds the fibers 4 on the diffusion section 7, in particular on the end face on the distal end 6. In this way, a scattering hood with a layer thickness S, which is approximately 10 μm here, is formed on the fiber surface O formed by the scattering material 20. The scattering material 20 is additionally enclosed in fig. 1 by a cover 26, which is likewise formed here only on the diffuser section 7 and forms the outermost cover of the device 2. In this context, the cover 26 is made of a biocompatible material, preferably glass, in view of the medical application, since this part is potentially in contact with tissue during application.

Fig. 2 shows partially one of the scattering elements 18 of the device 2 and illustrates by way of example a possible light path for light LT conducted in the longitudinal direction L in the core 14 of the fiber 4. Based on the design as a recess 24 filled with scattering material 20, the dual mode of action of the scattering element 18 is clearly evident. Light LT striking the boundary layer between core 14 and recess 24 first penetrates into scattering element 18, based on the difference in the refractive indices of the materials used, to be precise, and then obtains additional scattering due to the embedded scattering particles 22 in scattering material 20. In this way, light LT is coupled out of the fiber 4 at least partially in the radial direction R.

A suitable arrangement of a plurality of recesses 24 along the diffusion section 7 is shown in strongly simplified form in fig. 3a and 3 b. Here, fig. 3a shows a front view of the fiber 4. It is clearly apparent that the recesses 24 are arranged evenly distributed in the circumferential direction U, and are offset at an angle of 120 ° relative to one another. Fig. 3b shows a side view of the fiber 4, from which it can be seen that the recesses are also arranged distributed in the longitudinal direction L, more precisely at a distance a from one another, which here also varies in the longitudinal direction L. In the embodiment shown in fig. 3a and 3b, the notches 24 are arranged generally helically along the longitudinal direction L.

Fig. 3c shows an alternative arrangement of a plurality of recesses 24 on the diffusion section 7, wherein two

subsections

28a, 28b are formed, on each of which a plurality of recesses 24 is arranged. In the case of the existing

subsections

28a, 28b, the recesses 24 are each arranged at the same distance a, but the distance a on the distal subsection 28b is reduced relative to the distance a on the other subsection 28 a. In the distal subsection 28b, the intensity of the light LT is reduced by the partial scattering already taking place in the subsection 28a, so that more light LT must be coupled out in the radial direction R in order to achieve a uniform scattering intensity. Therefore, the recesses 24 are formed in a higher density in the distal subsection 28b, so that an increased scattering also occurs.

Fig. 4 shows the result of a calculation of the light intensity to be expected emitted in the radial direction R as a function of the position in the longitudinal direction L on the diffusion section 7. Here, the intensities are shown for three different configurations K1, K2, K3 of the diffusing section 7 and are respectively normalized. The first configuration K1, which is arranged on the left in the respective three-column combination, is used only for comparison of the fibers 4 without scattering elements 18. In contrast, configurations K2 and K3 show the desired emission for a diffusing section 7, which is constructed similarly to the example in fig. 3c with a plurality of, here three,

subsections

28a, 28b, on which in each case different distances a between the scattering elements 18 arranged one behind the other are present. The configuration K2 is shown for the result that only the notches 24 are machined into the fibers 4 of the scattering element 18 and is shown centrally in the respective three-column combination. The third configuration K3, which remains and is shown on the right, then shows the emission as a function of the position for the scattering element 18, in which the recess 24 is additionally filled with the scattering material 20. It is clearly visible that in configurations K2 and K3 a more uniform emission of light LT is achieved compared to configuration K1 due to the diffusing element 18 over the entire diffusion length DL of the diffusing section 7.

Finally, fig. 5a to 5d each show a step of a method for producing the device 2, in particular the diffusion section 7, by processing the fibers 4. The sequence of the steps in the method corresponds here to the sequence of fig. 5a, 5b, 5c, 5 d. First the fibres 4 are provided as shown in fig. 5 a. The fibers are shown in elevation here and in subsequent figures. Fig. 5b shows the machining of the recess 24 by means of a laser, not shown in detail, whose laser radiation LS removes a portion of the fiber 4. In this way, a recess 24, here substantially spherical, is produced.

Next, as shown in fig. 5c, a scattering material 20 is applied to the fibers 4, which scattering material comprises a matrix made of a base material, preferably silica gel, into which scattering particles 22, in particular nanoparticles made of aluminum oxide, are embedded. Fig. 5d then shows how an outer cover 26 is then applied to the entire arrangement, which here completely surrounds the diffusion section 7 and thus prevents the scattering material 20 from coming into contact with the surroundings.

List of reference numerals

2-fibre optical device

4 fiber

6 distal end

7 diffusing segment

8 coupling-in terminal

10a first coupling element

10b second coupling element

12 control unit

14 core

16 covers

18 scattering element

20 scattering material

22 scattering particles

24 recess

26 outer cover

28a sub-section

28b distal subsection

Distance A

D extension dimension

DL diffusion length

Fiber diameter of F

Diameter of K core

K1, K2, K3 configuration

L longitudinal direction

LS laser radiation

LT light

Surface of O fiber

R radial direction

Thickness of S layer

Depth of T

U circumference direction

Wall thickness of W

Claims

1. A fiber-optic device (2) for radially coupling out light, which is designed as a probe that can be inserted into a cavity, comprising an optical fiber (4) which extends in a longitudinal direction (L) to a distal end (6) and has a core (14), and comprising a diffusing section (7) in which a plurality of scattering elements (18) are arranged, which protrude into the core (14) in each case,

wherein the scattering elements (18) each have a recess (24) with an opening or a hole for filling on a fiber surface, wherein the fiber surface is a surface of a cap (16) surrounding a core (14) when the optical fiber (4) has a cap (16) with a lower refractive index,

wherein a scattering material (20) is applied at least locally to the fibers (4), said scattering material having a matrix with scattering particles (22) embedded therein for scattering Light (LT),

wherein the recesses (24) are filled with the scattering material (20) and/or the fibers (4) are continuously coated with the scattering material (20).

2. A fiber-optical device (2) for radially outcoupling light according to claim 1, characterized in that the device is configured for in vivo medical applications.

3. Fiber-optic device (2) for radially outcoupling light according to claim 1 or 2,

the fiber (4) has a sheath (16) with a lower refractive index surrounding the core (14), and

the scattering elements (18) project from the surface (O) of the fiber (4) through the cover (16) into the core (14).

4. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the scattering elements (18) each have a spherical recess (24).

5. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the scattering elements (18) are each constructed as a region of the core (14) with a modified refractive index.

6. The fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the scattering particles (22) are configured as nanoparticles and/or the scattering material (20) has a fraction of scattering particles (22) in the range of 1 to 10 vol.%.

7. A fiber-optic device (2) for radially outcoupling light according to claim 6, characterized in that the scattering material (20) has a fraction of scattering particles (22) in the range of 2 to 5 vol.%.

8. A fiber-optic device (2) for radially outcoupling light according to claim 6, characterized in that, when the scattering particles (22) are configured as nanoparticles, the nanoparticles have an average diameter between 10 and 100 nm.

9. A fiber-optical device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the fiber is a PCS fiber or an HPCS fiber.

10. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the recess (24) has an extension dimension (D) in the range of 20 to 500 μ ι η and/or the recess (24) has a depth (T) in the radial direction (R) in the range of 15 to 450 μ ι η, respectively.

11. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the recess (24) has an extension (D) in the longitudinal direction (L) in the range of 20 to 500 μ ι η.

12. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the notches (24) are arranged distributed in the diffusing section (7) in the circumferential direction (U) as well as in the longitudinal direction (L) of the fiber (4) for emitting Light (LT) uniformly in the radial direction (R).

13. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the notches (24) are spaced apart with respect to each other along the longitudinal direction (L) with a pitch (a) in the range of 100 to 1000 μ ι η.

14. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the notches (24) are spaced at varying pitches (a) relative to each other along the longitudinal direction (L) for evenly emitting Light (LT) along the longitudinal direction (L), wherein the pitches (a) decrease towards the distal end (6).

15. A fiber-optic device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the fiber (4) is surrounded by a housing (26).

16. A fiber-optic device (2) for radially outcoupling light according to claim 15, wherein the housing (26) is a glass capillary tube closed at the end side.

17. A fiber-optical device (2) for radially outcoupling light according to claim 1, characterized in that the device is configured for one of a group of applications comprising: medical diagnosis, medical treatment, illumination of a component or workpiece, and inspection or processing of a component or workpiece.

18. A fiber-optical device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the fibers have a diameter in the range of 125 to 1500 μ ι η.

19. A fiber-optical device (2) for radially outcoupling light according to claim 1 or 2, characterized in that the continuous coating of scattering material produces a scattering hood surrounding the fibers in the region of the diffusing section.

20. Method for manufacturing a fiber-optical device (2) for radially outcoupling light according to one of claims 1 to 19, wherein a fiber (4) is first provided and a plurality of notches (24) are machined into the fiber by means of a laser, wherein subsequently a scattering material (20) is applied at least locally onto the fiber (4).

21. The method according to claim 20, characterized in that the recess (24) is filled with the scattering material (20) when the scattering material (20) is applied.